I have only done it with an Igloo cooler and the fake ice packs. The more insulation, the longer it can stay cool, so the styro will not last as long.

I brought cupcakes to my family reunion last year and the Igloo coolers lasted from 8 am to into the night. I still had to set them out for about 15 minutes to taste good. It was about 100 degrees. I did put the coolers under the table to keep the sun off.

You should be fine at 80 degrees for at least 6 hours. You could have the cupcakes cool to start by popping them in the refrigerator for about an hour.